A Direct Demonstration of the Catalytic Action of Superoxide Dismutase through the Use of Pulse Radiolysis

Abstract Superoxide dismutase catalyzes the decay of O2-, generated by pulse radiolysis. The enzymatic reaction was first order with respect to enzyme and to O2- and the rate constant, which was 2.3 x 109 m-1 s-1 at pH 7.0 and 20–25°, was not much affected by pH, in the range 4.8 → 9.5. Boiling the enzyme or reversibly removing its copper prosthetic group caused loss of catalytic activity. EDTA had no effect on the enzyme-catalyzed dismutation of superoxide radicals, but did eliminate catalysis by Cu++.